Two-chamber syringes are being developed inter alia as a form of administering medical preparations when individual components of the preparation are only stable for a short time for the application when they are mixed with one another, and therefore must be separated from one another for the time period of lengthy storage. A widely encountered example of this is that of freeze-dried preparations, in which active substances sensitive to hydrolysis are separated from the solvent for the storage time and are only reconstituted to form the solution directly before the application. In principle, there are two possibilities here for combining the components, on the one hand the liquid/liquid combination and on the other hand the solid/liquid combination. Two-chamber syringe systems have the advantage that the mixing of the two components can take place without decanting into another container and that administering can then be performed directly from the container. In the form of two-chamber carpules, the containers can be inserted into syringe holders or injector systems (pen systems or autoinjector systems) that are provided for them and can possibly be used repeatedly. As a two-chamber syringe, the container is prepared with a molded-on pushrod or a pushrod screwed into the plunger or a plunger rod for advancing the plungers and with or without a fitted injection needle.
For the application, for example parenteral application, syringe devices such as for example disposable syringes or carpules generally first have to be vented. This step is problematic in particular in the case of automatic dispensing from injector systems, since an uncontrolled escape of highly potent pharmaceutical active substances must be avoided.
U.S. Pat. No. 5,971,953 describes a two-chamber syringe with a lower plunger (lower piston), an upper plunger and a cylindrical shaft (tubular member), gas in the mixing chamber being able to escape through a membrane in the lower plunger and an opening in the cylindrical shaft (opening). The two-chamber syringe described in U.S. Pat. No. 5,971,953 has the disadvantage that venting requires a tubular construction (shaft) for carrying away the air trapped in the syringe through the second plunger. The cylindrical shaft required for this extends the length of the syringe construction by at least the distance to be covered within the syringe cylinder. A combination with autoinjectors leads as a result to disadvantageous dimensionings, which are problematic with respect to suitability for marketing. Further disadvantages are the highly complex production and assembly of the two-chamber syringe as a result of the large number of individual components.
DE 102004055870 describes a single-chamber syringe comprising a cylinder element and a plunger device, a fluid-tight, gas-permeable element being arranged in the plunger device and allowing gas that is in the cylinder element to be removed through it when the plunger device is introduced into the cylinder element.
EP 1237596 B1 describes a single-chamber syringe unit comprising a syringe body with a discharge end, a plunger movably arranged within the syringe body and a connecting tube, which has a distal end and a first end, which is connected to the discharge end of the syringe body, the tube having a venting cap with a throughflow preventer, and the throughflow preventer being gas-permeable, but fluid-tight, and can be formed as a membrane or as a shut-off valve (check valve). The throughflow preventer serves for venting the syringe after filling of the syringe and before connecting of the connection tube to the patient.
WO 2006007592 describes a syringe system with a front chamber for receiving a liquid and a rear air-filled chamber, it being possible for air to be admitted to the rear chamber under sterile conditions by way of a filter membrane and an opening.
U.S. Pat. No. 4,373,535 describes a single-chamber syringe for the removal of blood samples, comprising a suitable syringe body and a plunger device, the plunger device containing a gas-permeable, but liquid-tight membrane, which serves for venting. The membrane used in U.S. Pat. No. 4,373,535 consists of a gas-permeable paper, which on contact with blood swells and stops further flow of blood. As in the single-chamber syringe described in DE 102004055870, the arrangement of a gas-permeable membrane in the plunger is not expedient for dual-chamber syringes, since here the storage stability is problematic in lengthy storage on account of gas permeation between the two chambers and from the rear chamber into the surroundings. The use of paper membranes is also not suitable as a barrier for maintaining a sterile state throughout the storage time.